It is crucially important to differentiate between fact and opinion when reviewing any kind of data or documentation. Facts cannot be disputed, and provide the empirical evidence needed to draw direct conclusions from your work.
However! That is not to take anything away from the role that opinion can play...
Opinion is the basis with which thought and knowledge progresses. Opinion is an idea which can then be tested and proven or disproven. Facts can only emerge by investigating what we do not know.
If we view facts as being Quantitative data - facts, figures, numbers etc. And opinion being Qualitative data - anecdotal, experience based etc, then of course we must also consider the subject matter when deciding which option is better. Sometimes the facts do not tell the whole story:
Think of a hard fought soccer match where one team completely dominates the other throughout the match, but in the final minute the team who have been the stronger score a freakish own goal, giving victory to the other side. In this case the scoreline does not tell the full story.